The present invention relates in general to a method and apparatus for supplying power to an automotive multimedia/personal computer system, and, more specifically, to a power management fault strategy for detecting fault conditions and restoring proper operation without user intervention.
Power management is an important issue in portable computing devices. This is especially true in mobile vehicles which have a limited battery capacity and which have stringent current limitations. As microprocessor-based systems become more powerful by using larger microprocessors and using a greater number of peripheral devices, power requirements increase. In vehicles containing an internal combustion engine and alternator, electric power generation may be sufficient to operate without much difficulty. In vehicles using other power plants or in an internal combustion engine vehicle with the engine shut off, significant limitations may be placed on current consumption (both normal operating current and quiescent current) of the multimedia/PC system.
Partly due to available power limitations, microprocessors having low power requirements are normally used in mobile vehicles. As mobile computing functions have been introduced into vehicles, reduced instruction set computing (RISC) microprocessors have been chosen since they are smaller and consume less power. Thus, complex instruction set computing (CISC) microprocessors such as Intel Pentium (x86) microprocessors and the Motorola 680x0 family of microprocessors have been avoided. However, RISC microprocessors often cannot run the same software as has been created for CISC microprocessors. Availability of operating system and applications software is much greater for CISC microprocessors because of the popularity of desktop and laptop personal computers. Therefore, it would be very beneficial to use a CISC microprocessor in a mobile vehicle.
An important performance issue for a multimedia/personal computer based system in a mobile vehicle is boot-up time. A multimedia system may be providing information, communication, entertainment, or other functions which the vehicle user may expect to be available as soon as the vehicle ignition switch is turned on. By example, the multimedia system may include a navigation function and the driver may want to initiate input of a desired destination as soon as possible after turning on the vehicle. By maintaining full or partial power to the multimedia system, boot-up time can be reduced or eliminated, but this conflicts with the need to minimize power consumption. CISC microprocessors such as the Pentium typically have reduced power states in which processing operations are suspended while the state of the memory and the internal microprocessor state are stored. Such a reduced power state may be entered in response to various conditions monitored by the microprocessor. However, the microprocessor can""t go completely to sleep and still monitor the conditions which should wake it up. Furthermore, if the microprocessor has sole responsibility to conduct its own power management, then there is limited ability to recover from errors.
Co-pending application U.S. Ser. No. 09/353,685 describes a vehicle input/output processor (VIOP) using a low power microprocessor to manage power for a main application microprocessor. Various operating states of the main application microprocessor and the low power microprocessor facilitate low current consumption while a vehicle ignition is off, fast boot-up times when the ignition is on, and intermediate boot-up times if the ignition has been off (but not if it has been off for a long period of time, such as 24 hours). However, if the main application processor malfunctions, the proper operating states may not be obtained and unacceptable current consumption may result.
The present invention has the advantages of providing efficient and robust power management of an in-vehicle multimedia/personal computer-based system, while detecting fault conditions and restoring proper operation without user intervention.
In one aspect of the invention, a method of powering a vehicle information, communication, and entertainment system is provided for mobile operation of information, communication, and entertainment devices in a vehicle. The vehicle has a vehicle powered state and a vehicle unpowered state. The method includes operating a power management chipset mounted on a main motherboard to control power to a main application microprocessor and a random access memory mounted on the main motherboard. A plurality of regulated voltages are supplied from a power controller and regulator to the power management chipset. The regulated voltages are switched on and off under control of a reduced power microprocessor in response to the user control and whether the vehicle is in the vehicle powered state or the vehicle unpowered state. A status message is periodically transmitted from the main application microprocessor to the reduced power microprocessor during normal full-powered operation of the main application microprocessor. A predetermined time period is established in the reduced power microprocessor during which a status message is expected to be received from the main application processor. A reset signal is sent from the reduced power microprocessor to the main application microprocessor if the status message is not received during the predetermined time period.